Write a function that provides change directory (cd) function for an abstract file system.

path.php

<?php
class Path  {
    
public $currentPath;

    function __construct($path) {
        $this->currentPath = $path;
    } 

    public function cd($newPath) {
        $innerCounter = 0;
        $strOut= '';
        $newPath = explode('/',$newPath);
        $oldPath = explode('/', $this->currentPath);
        
        foreach($newPath as $str) {
            if($str == '..') $innerCounter++; 
        }
        
        $oldLength = count($oldPath);        
            for($i=0;$i<($oldLength - $innerCounter);$i++)
                $strOut .= $oldPath[$i]."/";
        
        $counter = 0;
        $newLength = count($newPath);        
            for($i=0;$i<$newLength;$i++){
                if($newPath[$i] !='..'){
                	if($newPath[$i] != NULL){
                		if($counter){
                    		$strOut = $strOut."/".$newPath[$i].'';

                		} else {
                    		$strOut = $strOut.$newPath[$i].'';
                		}
                		$counter++;
                			
                	}
                	
                }
            } 
            
        $this->currentPath = $strOut;    
        return $this;  
    }

}

$path = new Path('/a/b/c/d');
echo $path->cd('../x')->currentPath;

Still fails for 3 Three times up: Wrong answer on https://www.testdome.com/questions/php/path/7265?testId=30&testDifficulty=Hard
Example case: Correct answer
Two times down: Correct answer
Three times up: Wrong answer
Complex paths: Correct answer